Coupling arrangement



, ter of Athe square.

zum@ sms PATENT @fi-FICE YcoiUPLiNG "ARRANGEMENT HcnriG. BusigniesgForest Hills, Trevor H. Clark,v NewYork, andi Arbor G. Everhart, Isl ip, N. Y., assignors to Federal `Telephone and RadioCori i i poration, Newark, N. J., a corporation of:Dela-.

Waffe f 1 "y Appi'iminAugusfae194s,seriaiigoitiiacis 4 Claims. (c1. zsoedim VThis invention relates to coupling i arrangev ments and in particular toicircuit arrangen'ients for coupling a plurality of receivers to a` low` impedance transmission line.` i

i Among the'objects'of our invention are:

To provide aneiective coupling circuitfor use-i` such asV between a low impedance transmission li'n'e and a radio receiverrv i I provide betweei'fi` a `low impedance .trans-` ii'iission `line and `a receiver]V a"coupling means having characteristics ysuclrrth'at the veiifect ofV the circuit `is 'i substantially `balantied;

fTof-provide aplurality of coupling means between alowimpedanee transmission line anday p lllaltyffOfQ receivers w'lfiichwill` substantially prevent inter-actionjbetween the receivers.

` jTo provide between' aradio direction finding system and alplurality of .receivers" a coupling means havingcharacteristics such thatthere is substantially'no inter-action' between` the re-W ceivers and thelidirection iin` diifig system.

. These and other objects fof our invention will best be understood by the following description of` a preferred `ernloodiiner'it thereof, describedfor purposes of illustration `and shown in the acco 1r 1f panying drawing. i

' the drawing we have represented by reference ynumeral 2 "a ydirective iantenna 'systemof theAdcock type having four ymonopole antennas 4,6; 8, and Il! positioned onthe corners of a square in a usual manner. v A monopole sensing antenna I2 is positioned in thegeometrical cen-V Between the monopoles and ground are antenna coupling unitsl I4, I6, I8, 2i!

and 22. These coupling units may be of the ktype described in acopendingBusignies "application C Veri'cnfthe transmissionlineis substantially iii) serial Number 481,760 iiied April 3, 1943, now i Patent No. 2,434,904 granted January 27, 1948 and comprise vacuum tube amplifiers `of the cathode `follower' type. As described in said copending application these coupling units have an 4rlpilt impedance suitablefor matchingthe impedanceiof theantennas to which they are' connected and` af'i'elativelylow output impedance suitable'for matching the impedance'of a low impedance transmission line to-which the output `of `said coupling unit isconnected.

In accordance "with the teaching of acopending Bsignies application'Serial 10,445,468 led June 2,-1942,1zidw-1=atent No'. 2,424,968 granted 'August 5, 194'7,` transmission lines represented by refer-V encenumerals 2li,l Z6 extend from the coupling unitsM andj I8 and at right anglesfto the plane of the antennas 4 and 8. These. transmission lines are crossconnectedat the point 28 where they connectA with a further transmission line 30- which extends to a direction finding receiver 32 located at a distant"'point. `The' characteristics of these transmission lines are such that a suitableimpedance matchv occursfat-thepoint 28. vIn

`the drawing we haveschernatic'ally represented extending .to the'direction finder receiver 32. As

described in copending application 445,468 this construction 'of transmission lines inthevicinity of the antenna system is for thepurpose of reducing polarization effects.

,From the L ccupling. 'unit `22 connected with sensingantenna I2` there is ajbalanced tran-smission 'line comprising'`conductorsll2 and 44 also extending to'the direction finder receiver. This balancedjlinecould alsobe an unbalanced coaxial linebutforthe purpose of this description we have'l illustrated aline ofthe balanced type in `order to illustrate certain features "of our invention; jj

` The directioninder receiverm'ay beV of the. type and comprise the units described in a Busignies and Richardson 'application Serial Number 400,154-ld vApril 23, 1942, now abandoned. 'The specic construction of` the direction `finder receiver constitutes no part of our present invention.` vIn any direction, nding systemof the type fillustratedinwhich low impedance transmission 'lines extend between the yantenna system `and the receiver it has heretofore been considered "undesirable to 'connect yany apparatus to these fever, other'antennas'located in the vicinity of the direction finding `antenna. system might prove rangement having Acertain desirable .properties in accordance with our invention, it is Vpossible to connect either a single receiver or a plurality of receivers to the transmission lines of a direction nding system Without upsetting the balance or in any other way destroying the accuracy fof -the direction indications. In the vdrawing, .the coupling arrangement comprises the .vacuumtube amplier shown within the dotted'lolock 46. v"11h-e amplifier comprises a vacuum ltube '48 #having cathode, control grid, and plate electrodes, 50, 52 and 54 respectively and also ascreengrid .5.6 rand a suppressor grid 58. Between the cathode and ground and between the anode and ground rthere are resistors 60 and 62 respectively. Resistor 60 is .in Ythe .input ycircuit of the amplifier whileiboth resistors 6,0 vand '62 arein A'the output circuit thereof. :Capacitor 64 sservesas acoupling .between the amplifier-and the conductor .44 of -the transmission `line Ibetween the -sensing antenna and the direction iiriderreceiver.V :fResistorfBisfa grid leak. A :positive lpotential is applied to v-.the anode .54 `andalso tto the .screen=.grid ,55, the potential to the latter-being supplied .throughiresistor A68. :Capacitors 1U .and ZH b y-pass .radio frequency .currents toground. .Capacitors 1.2. and 14 serve as coupling reactors between the output of .the -amplifier .and .the 4receiver 15. The Sreceiver 1.6 .may .be .of .an-y cknown .type capable Iof being -tuned to anysfrequencysina widerequency band. It will be noticed that there arene tuning elements betweenthereceiver 1,6 .and the .antenna .I 2 with fwhich A.it ,is associated, .all .circuits between said antennafand .saidreceiver .being of an aperiodic character.

Due to the `charzlicterof .the amplifier,circuit which splits the phase .of an .input A.voltage .and produces .twooutput voltages, rone positive .and one negative with .respect .tolground thereaction betweenthe output .and .input '.circuits .is very small. For example, if 1.a positive potential ,with respect to ground appears on .lcontrol l.grid ..52, .a positive `potential .also t.appears .in `the output eircuit .between the .resistor .60 yand Ithe cathorle ,5.0.. However, va negative .potential .with Arespect .to ground .appears .inthe output circuit 4`betweenthe resistor T62 and the anode 15.4. Thesepositiveand negative potentials. tend .to neutralize each other in their reactiononthe control. grid .52 inthe .input circuit. These positive .and .negative-potentials are also coupled to and actuate receiver 1.6 through `the coupling capacitors '1.4 and 1.2 respectively.

.The neutralization from .the output .to Athe .input circuit maybe .made substantially complete by connecting .twoneutralizingf capacitors l8.0 and '82 'betweenthe plate and controLgrid and between the cathode and control grid respectively. The rotor plates of .these capacitors .may be mounted Yon a common shaft .an'd so Epositioned with respect to .their corresponding stator plates that, as .the capacitanceof one capacitor increases ,the capacitance .of .theother-.capacitor .decreases. .By suitableadjustment .of .theneutraliz- 'ing capacitors Athe .eiiectivecapacitances.between .the .control grid .'52 .and the ,plate and .between the `control grid and .thecathode .mayfbe made substantially equal thus preventingthe transmission .of high ifrequ'ency .energy .through the tube .due .to capacitance effects. .1f it isfknollm Iwhich of the tube interelectrode capacitances is the smaller, a single neutralizing capacitor may be connected in parallel with the smaller interelectrode capacitance.

The input impedance of the amplifier is relativelyhigh, .preferably of =theorder of.5.000 ohms or more. This impedance'connected between the conductor 44 of the transmission line and ground fissso high that it practically has no influence on the relatively low impedance of the transmission lineand, therefore, produces substantially no unbalance Aof the latter.

:In thedrawing Wefhave also shown a plurality of 'other receivers and coupling units connected to the'low impedance lines V42, 44. These receivers and coupling units lmay be identical to the re- -ceiVer .16 and coupling unit 46 described above. Thev input impedance of all of the coupling units in parallel is still relatively very high with respect to the low impedance of the transmission line which-may be of lthe-'.orderbf 11251110.1430 ohms. Therefore-even thoughfa pluralityof receivers are connected tothe transmission line, thereisstill substantially no deleterious reaction. .We nhave shown a plurality of receivers, vspecically three, coupled :to the conductor 44 and La .like .plurality of .receivers :coupled to .the .conductor 42. In this manner any minor unbalance lwhich might possibly occur onone conductor .is compensated for -by a similar imbalance on qtheother conductor. It is to belunderstoodhowever, ,that

eilen --if there were .an -unequal numberof k receivers coupled to the two conductors of the balanced transmission line 4Z-44, ,any unbalancepf .the line .would b e .isosmall as to .have asubstantially negligible eiect. VFor the .reasonsabovedescribed whereby the reaction between theoutput andinput circuits `of .the .coupling .unit is -very small, there .is Aalso substantially .no reaction between any :two receiversof a pluralityof .receivers.con nected 4to `the .transmission `lines. VThis .is .true even though the various receivers are .tuned Ato thesame frequency. In suohacase anyreaction whicndoesoccur .is morelikely ,tolbe duetoother causes vsuch vas extraneous .coupling rather than to the fact A that the vireceivers are coupled .to-a

` common transmission line.

,Inthe 4drawing .we have. illustrated .the receivers as'connected to .the .line betweenthe .sensing antenna andthe directionhnderreceiver. fIhisiS preferable because of symmetry butthereceivers could also be .connected .to linesextending from theouter monopoles to the directionynderreceiv.- er. .Furthermore thedirection iindingantenna system could comprise `dipole .rather ,than fmonopol e antennas.

While we have described .above Y,the principle ofourinvention in vconnectipn Withspecic apparatus, it is Vto be clearly `understood y that .this description is made by way of example `.and not as a limitation .on .thescope of our .invention asset forth inthe objects thereoianditheaccompanyng claims.

We, claim:

.1. rIn combination, a \directi,on -,ndi1.i g :System comprisingansaperiodic v directionalfantenna sys- Atem Vand an aperiodic non-.directionalantenna tion finding receivenand coupled thereto,.aneven ,number of additional receivers, and-ay like number ofcoupling units, half of .said-.couplingzunits-,cou- .pling halfcf saidreceiversto onecpnductorzofrn of said transmission lines and the other half of said coupling units coupling the other half of said receivers to the other conductor of said one transmission line, whereby any interaction of one of said receivers with one of the transmission lines is balanced by a like interaction of one of the receivers coupled to the other of the transmission lines, with said other of the transmission lines.

2. The combination according to claim'l wherein each of said coupling units have a high impedance relative to the impedance of the transmission lines.

3. The combination according to fclaim 1 wherein each of said coupling units comprises a vacuum tube amplier having cathode,-'contro1 grid and anode eiectrodes, an input circuit connected between said cathode and control'grid, an output circuit connected between said cathode and anode, and neutralizing means connected between said output and input circuits to minimize reaction therebetween.

4. The combination recited in claim 1 wherein each of said coupling units comprisesa phase splitting vacuum tube amplier.

ARBOR G. EVERHART. HENRI G. BUsIGNIEs. TREVOR H. CLARK.

6 REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,313,483 Heising Aug. 19, 1919 1,853,181 Shumard Apr. 12, 1932 1,912,766 Esau June 6, 1933 1,971,235 Rettenmeyer Aug. 21, 1934 2,000,190 Rettenmeyer May 7, 1935 2,003,962 Weinberger June 4, 1935 2,006,994 Hopkins July 2, 1935 2,054,799 Kautter Sept. 22, 1936 2,129,075 Weinberger Sept. 6, 1938 2,147,807 Alford Feb. 21, 1939 2,179,414 Konkle Nov. 7, 1939 2,229,043 Butler Jan. 21, 1941 2,229,044 Butler Jan. 21, 1941 2,411,706 Berkoff Nov. 26, 1946 OTHER REFERENCES Bell Telephone System Technical Pub., Monograph B-893, entitled Radio-Frequency Distributing System, by F. X. Rettenmeyer. Al-so published in Proc., I. R.. E. v01. 23 pp. 1286-1307. 22 pp. text. pub., Nov. 1935. (Copy available in Div. 51.) 

